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What is current in a circuit?

the flow of charge

What is potential difference in a circuit?

measure of energy that is required to move a unit of electric charge between two points.

What is resistance in a circuit?

The opposition to the flow of electric current

What is ohm’s law?

Principle stating that electric current flowing through a conductor is directly propotional to the voltage (provided the temperature stays constant)

What causes electrical resistance in a wire?

The electrons colliding into the ions of the wire

How is the current distributed between components in a series circuit?

The current is the same for all elements

How is potential difference distributed between components in a series circuit?

The voltage is shared between the components. (v = v1 + v2)

How is resistance distributed between components in a series circuit?

The total resistance is equal to the sum of all individual resistances

How is current shared between components in a parallel circuit?

The current is shared between each component (I1 + I2 = I total)

How is potential difference distributed between components in a parallel circuit?

Thevoltage across all components are the same (V = V1 = V2)

What are the four factors that affect the resistance of a wire?

Length, thickness, temperature, and material

What happens when resistance in a circuit increase?

the current decreases

does a resistor follow ohm’s law?

Yes

Does a filament lamp follow ohm’s law? Why?

No, because the resistance is not constant.

What is the threshold value for a diode?

0.6V

what is a diode?

a component that only allows current to flow in one direction

What two things must be seen on a graph for it to be ohmic?

The line must be directionally proportional and go through the origin

What is an LDR and how does it work?

A light dependent resistor. They automatically change its electrical resistance based on the amount of light falling on it

What are control circuits used for?

A control circuit has components used to detect change. These components are sensors, for example thermistors.

What is a thermistor?

A highly sensitive temperature sensor made of semiconductor material.

How to thermistors work?

When it’s cold, the resistance increases. When it’s hot, the resistance decreases.

what are uses of thermistors?

fire alarms, central heating thermostats, thermometers

What are uses of LDRs?

Street lights, automatic car headlights

What is direct current?

current that flows in one direction only

What is alternating current?

current which repeatedly flows in one direction and then reverses its flow. The frquency is how many times it changes direction in one second. Used for mains electricity.

What is the current of the UK mains?

230v

what is the frquency of the UK mains?

50Hz

What is the earth wire? what colour is it?

wires that ‘earth’ appliances and redirect the current to the ground instead of to a person, if one of the wires touches the casings. It’s yellow and green

What is the neutral wire? what colour is it?

the wire that completes the circuit form the appliance to the back of the supply. Usually at 0V. usually blue in colour.

What is the live wire? what colour is it?

The wire that carries the 230V alternating potential difference from the power supply. Brown in colour

What does the fuse do?

stops the flow of current if it gets too high

Why do appliances with plastic casings not have earth wires?

because plastic is an insulator so there is no danger in the live wire touching the casings.

What is a transformer?

An electrical device that changes voltage into higher or lower voltages. aka step up and step down

Why do high voltages need to be lowered?

they’re too dangerous for domestic use

Descrive how electricity is transmitted

1.Electricity is generated at a power plant

2. Voltage is increased in a step up transformer

3. Electricity travels across land on trasmission lines

4. Voltage is decreased at a step down transformer

5. Electricity is carried on distribution lines

6. voltage is decreased before entering the home

how much voltage is trasmitted on the national super grid?

400,000V

Why is voltage increased?

Current decreases, reducing energy wasted in thermal energy

What is the national grid

The system used for distributing electrical energy around the country.

What is sublimation?

When a solid transforms into a gas, skipping the liquid phase

What is deposition?

When a gas transforms traight into a solid, skipping the liquid phase

What is specific heat capacity?

The energy required to raise 1KG of a material by 1 degree celcius

What is latent heat capacity?

the energy required to change the state of 1KG of a material without changing the temperature

What did John dalton discover?

That atoms are tiny spheres

What did JJ Thompson discover?

Discovered the electron and created the plum pudding model (discovery of the electron proved Dalton’s model was incomplete)

What did Ernest Rutherford discover?

That the atom is msotly empty space, positive charge is concentrated at the nucelus, electrons orbit the nucleus. He carried out the alpha scattering experiment

What did Niel Bohr discover?

electrons orbit the nucleus in fixed shells

What did James Chadwick discover?

the neutron

What are the 3 nuclear radiations?

Alpha, beta, and gamma

what is an alpha particle?

A helium atom. 2 protons, 2 neutrons

What is a beta particle?

A high speed electron

What is a gamma ray?

An electromagnetic wave

What’s a use of alpha particles?

smoke dectors because alpha particles are easily blocked

What’s a use of beta particles

Thickness gauging as its moderately penetrating

what’s a use of gamma rays?

steralisation, essentially mutates bacteria cells